1. Field of the Invention
The present invention relates to an electrostatic dust collector which uses a porous dielectric as a diaphragm between electrodes.
2. Description of the Prior Art
To eliminate microparticles floating in exhaust gases or the like, it is common practice to use a filter device which permits the gases to pass through a porous member and to collect the particles. This system, however, involves problems that if the pores of a particle collecting material are greater than a predetermined value, it is hard to collect the particles. If the thickness of a collecting material is made larger, the resistance to the passage of fluids therethrough increases and increases the pressure loss. There is a limit in dust collecting performance in such filter devices.
On the other hand, for the purpose of eliminating air pollution from smoke or the like, an electrostatic dust collector has been used in which microparticles in gases to be eliminated are charged in a corona discharge area. The charged gas particles are passed between plates to which high voltage is applied and the charged particles are electrostatically absorbed. This system allows microparticles having a diameter of approximately 0.1.mu. to be collected pressure loss resulting from said dust collector is very small. However, this system suffers disadvantages in that a corona discharge section and a collecting section must be provided. This results in a complex construction. Furthermore, if the collecting performance is increased, high voltage must be used or the voltage applied section has to be extended. Concentration of electric fields on a raised portion of microparticles accumulate on the plates and causes a discharge to again scatter the collected microparticles.
There is a further problem in that, if any of these devices are installed in an existing duct or the like, such device has to be specially designed to meet the size and shape of the duct.
Moreover, in such devices, as described above, the collecting plates are exposed. The durable period is extremely short if they are used in corrosive environments. Because of this, the devices have been difficult to use, not only in installations involving exhaust gases in boilers containing SO.sub.x but in hospitals, animal breeding farms and the like where formaldehyde solutions containing methanol and similar solutions are used.